1. Field of the Invention
The invention relates to toroidal accelerometers and more particularly to a temperature compensated toroidal accelerometer with means provided to prevent polarization of the electrolytic fluid.
2. Description of the Prior Art
In copending application entitled "Temperature Compensated Toroidal Accelerometer" , Ser. No. 524,594, filed on Nov. 18, 1974 in the names of Buckley et al and assigned to the assignee of the present invention, a toroidal accelerometer or tilt sensor is disclosed in which an auxiliary electrode is added for temperature compensation purposes. More particularly, the auxiliary electrode is disposed in the sensor so that it is completely immersed in the electrolytic fluid at all times. Furthermore, the auxiliary electrode is electrically coupled to the output of an amplifier which detected the rotation or tilting about the reference axis.
Prior to the incorporation of this auxiliary electrode, the output of the amplifier was dependent on the temperature related characteristics of the electrolytic fluid. The addition of this auxiliary electrode, in place of a fixed resistance, provided for a temperature dependent parameter in the amplifier circuit which has the effect of cancelling the existing temperature dependent parameter therein.
However, this arrangement is subject to limitations. For example, any d.c. or steady-state potential developed by the amplifier and its output is coupled to the auxiliary electrode and, therefore, to the electrolytic fluid as well. If the d.c. potential reaches an appreciable level, typically in excess of a few hundred millivolts, polarization of the electrolytic fluid begins. If the polarization of the electrolytic fluid is allowed to continue, the accelerometer will be rendered inoperable within a short period of time.
In an attempt to prevent the polarization of the electrolytic fluid, the prior art incorporated a potentiometer to null the d.c. output of the amplifier. However, this technique is sensitive to time, temperature and changes in the impedances between the electrodes within the accelerometer.